Surging Idle Upon Braking - 89 Pickup

Hi all, I drive a 89 Toyota pickup with the 22re motor. I recently noticed that when I start the truck up it idles real high and then slowly works its way down on idle. When I apply the brakes before the motor warms up, the idle drops and then starts to surge unless I tap the gas. Once the car is warm the issue goes away. I was told it could be brake booster leaking or the IAC needs cleaning. Has anyone had this issue?

 

Your idle is probably set too high. The ECU cuts fuel while braking when rpm’s are above ~1000. If you adjust the idle set screw so the idle is below 1000 rpm it should go away. Also if you have a fluctuating idle, the o ring on the idle set screw may be all dried out. You can replace that for cheap.

 

The issue is only when I first start the truck and wait for it to warm up, after that it doesn’t surge while driving or at a stop. This issue only just started a day ago and i’ve had the truck for while with no problems. Would it still be the same thing you just suggested

 

The ECU on these trucks is pretty simple. If you step on the brakes and the rpm’s are above a set point it cuts fuel. If it’s only an issue while warming up, it may not be the idle adjust screw, but it still sounds throttle body related. Have you cleaned your throttle body? What’s the idle set at when you warm up?

 

I honestly have no idea, the truck has no Tachometer so i don’t know the RPM it idles at. Throttle bottle has not been cleaned before from my knowledge.

 

Sounds like a leaking brake booster, do you hear any hissing when you step on the brakes?

 

I haven’t heard any hissing but the truck is also kinda loud, should i have a friend press the brakes while i listen to the brake booster? and should the truck be running or off while I check it?

 

UPDATE: I drove it once i finished my class and upon startup it would surge in idle at different rpms depending if I was pressing the brakes, If I press and held the brake, Rpms would drop and it would surge faster, if brake was not pressed, the surging stay the same. When I started to drive it and got to the first stoplight, the issue was gone. Only happens on startup now